Dyno, Dyno on the wall....an update

[orabanda]

Hi Olev,
Testing yet to be concluded on the first bike (my late father's 51 A10), due to 8 degrees variance between pot on the timing (when the results below wee achieved). However, I have it down to 1 degree now, so bike will be back on the dyno by the time we have won the ashes (in a few weeks!). The carb is totally set up (after 1 1/2 hrs run time.

My slotted maggie will give 20 degrees adjustment when on the bike, so I will be able to establish the optimum timing point for the engine

Pistons = 7.25: 1
Cam = 356
Compression = 150 psi each pot.

My target is 20 BHP (at the rear wheel)!

Thanks to Ray Moore Motorcycles.








The BHP figures are rear wheel

[Richard]

I must have missed some previous posts,
I can see that it is a SRM degree disc so I should be able to get one and on a swing arm engine I guess I could drill and tap two holes in the cush drive nut to take the disc having elongated the fixing holes in the disc so as to adjust for top dead centre and making a decent pointer as in the picture should be possible.
my questions are as folows
1) is there anyway by looking on the crank i.e. a keyway or similar to be sure it is at tdc?
2) how would you go about setting the timing with a strobe presuming the mag holes had been elongated for adjustment?
There must be some one that has found a sure way of determining true TDC on a A10 engine without taking the head of or using straws and the like?
Richard

[orabanda]

Richard,
TDC is easily (and accurately) established.
The SRM kit includes a piston stop (replaces spark plug) and very clear instructions as to how to find TDC. It isa quick 5 minute process and extremely accurate.
I made the pointer; it is adjusted to indicate TDC.

For this machine, I locked the mag in the middle of the range of adjustment on the slotted holes (ie; 10 degrees adjustable either way of this point). The timing was set statically to 32 BTDC at the time, and I have the ability to advance or retard 10 degrees from that point.

When running, a strobe light can be used to check either cylinder. This will show: (a) any variance between pots (I had far too much) and (b) the auto advance in operation.

http://i302.photobucket.com/albums/nn82/orabanda/IMG_4803.jpg

http://i302.photobucket.com/albums/nn82/orabanda/IMG_4804.jpg

Richard

[chaterlea25]

Richard,
If you use a gizmo like my timing "plug" it will stop the piston dead in both the forward and backwards rotation of the engine, measure the degrees between these points
Divide by 2 and this will be true TDC, reset the disc to half the amount of degrees, check again to be sure!
The plug should stop the engine rotating equal amounts of degrees before and after TDC when the engine is rotated forwards and backwards.
Remove plug and then turn engine to TDC
Regards
John O R

[orabanda]

John,
The SRM stop works in the same fashion (it is a stop), and TDC is found just like you have done.
Accurate and quick (and cheap).
Richard

[olev]

Orabanda,
Thanks for posting the chart.
I don't know what you expected but I was a bit suprised.
Where do you think the auto advance cuts out? For some reason I always thought it was around 3000rpm.
The power and torque both took a dive about 2300rpm.
My guess is the timing is too far advanced. What are the springs on your atd like? For an experiment, I'd take a reading off your degree wheel at 2250 and then reset the timing to be fully advanced at that figure.
With any luck the power and torque will keep going up at 2300. Even with figures taken at the back wheel, thats a sad chart. He didn't get it mixed up with a vespa did he?
I'm willing to bet that when you use your slotted maggy to get an optimum tune, your graph will look nothing like that.
Please keep us informed, this is riveting stuff.
cheers

[coater87]

 Hi,

 Just a thought, but are you running with valve springs that your sure are good? I recognise the "choppy" look in the HP line, and have only seen that when you get valve float- but that was at much higher RPMs then what you are running. Could be way off here, but the look of that line is familiar...

 On a further look, it seamed to start around 2850 or so. That seams WAY to low for float, but if you had a bad spring it might be the culprit.

 Lee

[orabanda]

Lee,
Head was totally reconditioned 900 miles ago; included new Terry springs.

I am sure a factor is the excessive difference in firing point between the LH and RH cylinders.

Tuning the carb made a big difference (improvement) in the (meagre) performance, increased the max torqueand lowered it 200rpm on the curve. 

Ray Moore (the mechanic) wanted to achieve a HS AFR (air fuel Ratio) of about 13:1 when setting up the carby.

This is the data from the last of about 20 runs:


The runs were done in 3rd gear, so the top speed would correct to 151 km/hr

BD14200   BSA   A10 Golden Flash   1951
Ramp-rate: 090   Tacho ratio: 92.0:3000   Graph: BD14200.0020   13-06-09 / 11:39:03

Dynamometer Correction Information   
                  
Speed   Tacho [Rat]   Power   T.E.   IAT   HS AFR
km/h   rpm   HP   lb   degC   Petrol
56   1826      7.4      80    12.3   10.0
58   1891      9.1      95    12.2   10.0
60   1957     10.6     107    12.2   10.1
62   2022     12.1     118    12.3   10.6
64   2087     13.5     127    12.3   11.6
66   2152     15.0     137    12.3   12.5
68   2217     16.6     147    12.3   13.2
70   2283     17.5     151    12.2   13.9
72   2348     17.2     144    12.3   13.8
74   2413     17.2     140    12.3   13.4
76   2478     17.6     140    12.3   13.6
78   2543     18.0     140    12.3   13.5
80   2609     18.4     139    12.3   13.2
82   2674     18.7     137    12.3   13.2
84   2739     18.6     134    12.4   13.0
86   2804     18.5     130    12.3   12.8
88   2870     18.4     126    12.4   12.8
90   2935     18.3     123    12.3   12.9
92   3000     18.3     120    12.3   12.7
94   3065     18.0     115    12.3   12.6

96   3130     17.9     113    12.4   12.7
98   3196     18.2     112    12.3   12.7
100   3261     18.1     109    12.3   12.6
102   3326     17.9     106    12.4   12.6
104   3391     18.0     104    12.4   12.6
106   3457     17.7     101    12.4   12.6
108   3522     16.8      94    12.3   12.6
110   3587     17.4      95    12.3   12.6
112   3652     17.2      92    12.4   12.5
114   3717     16.6      88    12.3   12.3
116   3783     15.5      81    12.3   12.4
118   3848     14.4      74    12.4   12.4
120   3913     13.4      67    12.4   12.3
122   3978     13.3      66    12.4   12.3
124   4043     12.6      61    12.3   12.1
126   4109     11.5      55    12.4   12.1


The auto advance had just been replaced with an overhauled itemworked well; smooth, with full advance at approx 3,000 rpm.

Mind you, they must be Clydsdales, because the bike seems to have plemty of urge ; more grunt than an Afghan brothel!

Richard

[Clive54bsa]

Hi Orabanda, I've just recently set the timing on my '54 Golden Flash as per your suggestions, reduced the timing BTDC to about 30 and 1/2 degrees with about 1 degree difference between the two pots. The right one being the 1 degree more advanced. I was VERY meticulous, as I am recovering from a pinched nerve in my back, so I'm in no rush to ride yet. Whilst I had  the bike on the lift, I went through the 276 carb with a fine tooth comb to check for any anomalies, such as a blocked idle circuit etc. and sealed the carb flange with hi-temp silicone, to prevent any air leaks. So finally I fired it up today and went for a ride around the block. Well the bike accelerated well, and idled lovely, but I get spit back through the carb when I "blip" the throttle. This problem had dogged me ever since I first got the bike running from a basket case about 3 yrs ago. I've pulled the carb several times to make sure the fixed pilot jet is not blocked. I installed a 3 1/2 slide and the float level looks about right. Also the right hand pipe, at the head runs about 35-40 degrees F, hotter than the left side. bluing the exhaust pipe. e.g. the left side will be say 210, and the rt side about 250, and obviously just idling in my driveway with no air cooling it, even hotter. The airscrew makes no difference when you screw it in from say a turn and a half out. But does stall if I wind out the screw.. I've read your posts on induction bias, could this be the problem? And if so where to does one get the special gaskets from? The motor has 7:1 pistons, 356 cam and I set the tappets to 010 in and 012 ex.
Any ideas?

[orabanda]

Hi Clive,
There are more knowledgeable tuners than me on this forum, but the spit back sounds like mixture to me (too lean?).

Most the A10's of mine have one pot leaner than the other, but it has always been the LH!

I have purchased  induction bias (tapered) adaptors from Cake Street Classics.

Richard

[muskrat]

Yep that's an indication of a lean pilot or slide. Try the pilot first, screw in 1/2 turn. If no good try a larger pilot. Then if no joy try a #3 slide. Pilot jets are cheaper than slides.
That amount of heat differential is borderline to rectify or not. If the plugs look even I'd leave it.
Richard, I'd say your up there for a sandgroper.
Cheers

[Topdad]

'Fraid I (for one ) can't agree with you Richard ,about there being better tuners on the forum there may be but what you are doing is very meticulous and shouldn't be played down in any way,  although I'm a dyed in the wool plug hole pencil pusher ( Musky remember your moderator status ) for timing and it suits me ,I'm still very interested in what your doing and the way you are going about it .I'm particularly impressed with the elongated holes on the mag ,simple but effective ! I had a strope timing light and timing disc /pointer for my first 53 flash  back in 1966 ,our family friend and my mentor had a knack of making things and  I didn't appreicate it (callous youth ) and felt taking the timing side of to adjust or getting covered in flying oil didn't give me enough benefit to continue now had we been able to modify my magneto who knows perhaps I'd never have resorted to inserting pencils !!  Keep up the good work and interesting post best wishes BobH.

[Clive54bsa]

Hi Muskrat, for the '54 Golden Flash, with the 276, "the book" calls for a #4 slide, I managed to find a # 3 1/2 on Ebay, with no difference. The pilot on a 276 however is fixed, and I'd be a bit apprehensive about drilling it out, as I'd be stabbing in the dark, not knowing what size to open it up to. The plugs look fairly even. Maybe the carb is just "clapped out". I've seen new 276/GG... on the internet, but as my bike is in original condition, (minus 59 years of wear and tear) I'm reluctant to spring for a new carb.

Topdad, I totally agree with you, Orabanda's posts on timing and tuning, and the supporting graphs are very informative.

Clive

[chaterlea25]

HI Clive,
When you say float height "about right" how have you checked this?
The fuel height should be level with the bottom of the pilot screw hole
If the incorrect washer is fitted under the jet block it can block off the fuel feed to the pilot passage
likewise too thick a washer will lower the fuel height
Wear in the body or slide will weaken the slow running mixture

Make sure there are no steps or obstructions especially at the lower half of the carb to head joint
even a small step or gasket intrusion can spoil the low speed running

HTH
John

[muskrat]

G'day Clive.
Sorry mate, I didn't have my spec book with me.
I agree 100% with John, worn body (explains the pinched nerve) allowing air past the slide, leaning out both the pilot and slide settings. Time for a sleeve.
Cheers